Enhancing optical and resistive characteristics of MnFe2O4 spinel ferrite through Ni2+ doping: An advancement in structural refinement

Abstract

Spinel ferrites are highly notable magnetic materials with vast potential for applications in microwave and high-frequency transformer applications. Manganese ferrites (MnFe2O4) are selected for their excellent optical, magnetic, and resistive properties. This research presents a co-precipitation method for nickel (Ni2+) doping in manganese spinel ferrite (MnFe2O4) to advance structural refinement and subsequently enhance optical and resistive properties. It is confirmed that Ni2+ doping has affected the crystal lattice and possesses a single crystalline phase. The diffraction peak at 36.2° suggests increased Ni2+ ion incorporation, impacting unit cell dimensions, lattice parameters, and phase composition. The Ni2+ doping introduces the strong covalent M − O bonds at octahedral and tetrahedral sites which impacts the grain size to 20∼35 nm and crystallite size to 33.29–21.23 nm. Infrared analysis reveals that the increasing Ni2+ shifts the M − O stretch in the octahedral site to higher frequencies, indicating stronger and more covalent M − O bonding. The band gap reduction from 1.41 eV to 1.28 eV results from Ni2+ and Mn2+ ion substitution in the ferrite lattice, driven by sp-d exchange interactions with their localized electrons. The resistivity of MnFe2O4 is increased from 9.37 × 103 to 9.43 × 103 Ω m with Ni2+ doping. This effect is ascribed to the occupation of both octahedral and tetrahedral lattice sites by Ni2+ ions. This communication conclusively establishes nickel as the optimal dopant for spinel ferrite, showcasing its versatility for a wide range of applications.